Field
The present invention relates to a field effect transistor and a method of manufacturing the same, and a field effect transistor suitably used in a high-frequency band and a method of manufacturing the same.
Background
With an increase in frequency of a field effect transistor, shortening of a gate length thereof is advanced. On the other hand, when the gate length is shortened, a gate resistance increases. Unexamined Patent Publication No. 2003-115500 discloses, as a method of suppressing the gate resistance, a T-shaped gate electrode having a T-shaped sectional shape. Unexamined Patent Publication No. 2003-115500 discloses a gate electrode including an overlapping structure as a countermeasure against a short channel effect caused by shortening the gate length. In the overlapping structure, a gate end runs on an insulating film to make it possible to moderate an electric field generated between a source and a drain.
In the structure described in Unexamined Patent Publication No. 2003-115500, an interface between a semiconductor layer and an insulating film and a lower end of a gate electrode are disposed at the same level. Interface states occur on the interface between the semiconductor layer and the insulating film. For this reason, the structure described in Unexamined Patent Publication No. 2003-115500, electron conduction is easily influenced the interface states. Thus, electrons become to be easily trapped by the interface states, and pulse characteristics may be deteriorated.